Use this 25 ohm SPRT in the calibration lab for excellent stability. Inconel sheath, 500 mm x 6.35 mmTemperature range: -200 °C to 670 °C If you are indifferent between 25 ohm and 100 ohm, consider this 25 ohm SPRT - It is likely to be more stable in the long term. Customized dimensions available.